东海陆架盆地西南部烟囱构造与油气运聚关系研究

In recent years, chimney structure has been proved one of important indicators and a useful guide to major petroleum fields exploration through their exploration history both at home and abroad. Chimney structure, which has been called "gas chimney" or "seismic chimney", is the special fluid-filled fracture swarm, which results from the boiling of active thermal fluid caused by abruptly decreasing of high pressure and high temperature in sedimentary layers of upper lithosphere. Chimney structure is well developed in continental shelf basin of East China Sea, which indicates the great perspectives of petroleum resources there. However, the chimney structure also complicated the petroleum accumulation. So the study of chimney structure on its formation, its effect on occurrence and distribution of petroleum fields is very important not only on theoretical, but also on its applied research. It is for the first time to make a clear definition of chimney structure in this paper, and the existence and practical meaning of chimney structure are illustrated. Firstly, on the viewpoint of exploration, this will amplify exploration area or field, not only in marine, but also on continent. Secondly, this is very important to step-by-step exploration and development of petroleum fields with overpressure. Thirdly, this will provide reference for the study on complex petroleum system with multi-sources, commingled sources and accumulation, multi-stage accumulations, and multi-suits petroleum system in the overlay basin. Fourthly, when the thermal fluid enters the oceanic shallow layer, it can help form gas hydrate under favorable low-temperature and high-pressure conditions. Meanwhile, the thermal fluid with its particular component and thermal content will affect the physical, chemical and ecological environments, which will help solving the problem of global resources and environment. Beginning from the regional tectonic evolution characteristics, this paper discussed the tectonic evolution history of the Taibei depression, then made an dynamical analysis of the tectonic-sedimentary evolution during the Mesozoic and Cenozoic for the East China Sea basin. A numerical model of the tectonic-thermal evolution of the basin via the Basin-Mod technique was carried out and the subsidence-buried history and thermal history of the Taibei depression were inverse calculated: it had undergone a early rapid rift and sag, then three times of uplift and erosion, and finally depressed and been buried. The Taibei depression contains a huge thick clastic sedimentary rock of marine facies, transitional facies and continental facies on the complex basement of ante-Jurassic. It is a part of the back-arc rifting basins occurred during the Mesozoic and Cenozoic. The author analyzed the diagenesis and thermal fluid evolution of this area via the observation of cathodoluminescence, scanning electron microscope and thin section, taking advantage of the evidences of magma activities, paleo-geothermics and structural movement, the author concluded that there were at least three tectonic-thermal events and three epochs of thermal-fluid activities; and the three epochs of thermal-fluid activities were directly relative to the first two tectonic-thermal events and were controlled by the generation and expulsion of hydrocarbon in the source rock simultaneously. Based on these, this paper established the corresponding model between the tectonic-thermal events and the thermal-fluid evolution of the Taibei Depression, which becomes the base for the study on the chimney structures. According to the analyses of the gas-isotope, LAM spectrum component of fluid inclusion, geneses of CO_2 components and geneses of hydrocarbon gases, the author preliminarily verified four sources of the thermal fluid in the Taibei Depression: ① dehydration of mud shale compaction, ② expulsion of hydrocarbon in the source rock; ③ CO_2 gas hydro-thermal decomposition of carbonatite; ④magma-derived thermal fluid including the mantle magma water and volatile components (such as H_2O, CO_2, H_2S, SO_2, N_2 and He etc.). On the basis of the vitrinite reflectance (Ro), homogenization temperature of fluid inclusion, interval transit time of major well-logging, mud density of the wells, measured pressure data and the results of previous studies, this paper analyzed the characteristics of the geothermal fields and geo-pressure fields for the various parts in this area, and discussed the transversal distribution of fluid pressure. The Taibei depression on the whole underwent a temperature-loss process from hot basin to cold basin; and locally high thermal anomalies occurred on the regional background of moderate thermal structure. The seal was primarily formed during the middle and late Paleocene. The overpressured system was formed during the middle and late Eocene. The formation of overpressured system in Lishui Sag underwent such an evolutionary process as "form-weaken-strengthen-weaken". Namely, it was formed during the middle and late Eocene, then was weakened in the Oligocene, even partly broken, then strengthened after the Miocene, and finally weakened. The existence of the thermal fluid rich in volatile gas is a physical foundation for the boiling of the fluid, and sharply pressure depletion was the major cause for the boiling of the fluid, which suggests that there exists the condition for thermal fluid to boil. According to the results of the photoelastic simulation and similarity physical experiments, the geological condition and the formation mechanism of chimnestructures are summarized: well compartment is the prerequisite for chimney formation; the boiling of active thermal fluid is the original physical condition for chimney formation; The local place with low stress by tension fault is easy for chimney formation; The way that thermal fluid migrates is one of the important factors which control the types of chimney structures. Based on where the thermal fluid come from and geometrical characteristics of the chimney structures, this paper classified the genetic types of chimney structures, and concluded that there existed three types and six subtypes chimney structures: organic chimney structures generated by the hydrocarbon-bearing thermal fluid in middle-shallow layers, inorganic and commingling-genetic chimney structures generated by thermal fluid in middle-deep layers. According to the seismic profiles interpretations, well logging response analysis and mineralogical and petrological characteristics in the study area, the author summarized the comprehensive identification marks for chimney structures. Especially the horizon velocity analysis method that is established in this paper and takes advantage of interval velocity anomaly is a semi-quantitative and reliable method of chimney structure s identification. It was pointed out in this paper that the occurrence of the chimney structures in the Taibei depression made the mechanism of accumulation complicated. The author provided proof of episodic accumulation of hydrocarbon in this area: The organic component in the boiling inclusion is the trail of petroleum migration, showing the causality between the boiling of thermal fluid and the chimney structures, meanwhile showing the paroxysmal accumulation is an important petroleum accumulation model. Based on the evolutionary characteristics of various types of chimney structures, this paper discussed their relationships with the migration-accumulation of petroleum respectively. At the same time, the author summarized the accumulating-dynamical models associated with chimney structures. The author analyzed such accumulation mechanisms as the facies state, direction, power of petroleum migration, the conditions of trap, the accumulation, leakage and reservation of petroleum, and the distribution rule of petroleum. The author also provides explanation for such practical problems the existence of a lot of mantle-derived CO_2, and its heterogeneous distribution on plane. By study on and recognition for chimney structure, the existence and distribution of much mantle-derived CO_2 found in this area are explained. Caused by tectonic thermal activities, the deep magma with much CO_2-bearing thermal fluid migrate upward along deep fault and chimney structures, which makes two wells within relatively short distance different gas composition, such as in well LF-1 and well LS36-1-1. Meanwhile, the author predicted the distribution of petroleum accumulation belt in middle-shallow layer for this area, pointed out the three favorable exploration areas in future, and provided the scientific and deciding references for future study on the commingling-genetic accumulation of petroleum in middle-deep layer and the new energy-gas hydrate.

库车坳陷第三纪磁性地层和磁组构的研究

The Tertiary Kuche depression, also known as one of the most economically important oil and gas prospecting regions in the Tarim Basin, is a foreland basin formed by flexural subsidence resulting from the southward thrusting of the southern Tianshan. Detailed geological and geophysical studies on the Tertiary sequence of the Kuche region would provide constraints not only on the Mesozoic and Cenozoic deformation patterns, and its controlling on the formation and distribution of oil and gas of the Kuche depression, but also on the India-Asia postcollisional uplift and continental deformation of the Tianshan regions. In this thesis, the Tertiary sequence of the Kuche depression, which is composed of the upper Kumukeliemu Formation, Suweiyi Formation, Jidike Formation, Kangcun Formation, and Kuche Formation, was selected for magnetostratigraphic and anisotropy of magnetic susceptibility (AMS) study. Among a total of 697 collected sites, 688 sites gave magnetic fabric results and 686 sites yielded reliable paleomagnetic results, building up magenetostratigraphy for the Tertiary sequence of the Kuche depression. By correlating with international geomagnetic polarity timescale, the followings were concluded: 1) the time interval of the sampling sections is some 31-8.1 Ma; 2) the boundaries for Kangcun/Jidike Formations, Jidike/Suweiyi Formations, and Suweiyi/Kumukeliemu Formations are at about 13.5 Ma, 26 Ma and 29 Ma respectively; 3) the Jidike Formation might be formed in an interval between the late Upper Oligocene and middle Miocene, whereas the Suweiyi Formation was formed in the Upper Oligocene, in turn, the Paleogene/Neogene boundary is most likely to be at the bottom of the Jidike Formation in the Kuche depression; 4) the dramatic transition from the marine/lacustrine to fluvial/alluvial facies in the Suweiyi Formation and the lower Jidike Formation of the Kuche depression, which may indicate the initiation of Cenozoic thrusting in the Kuche depression, is probably occurred in the late Oligocene, i.e. at about 28-25 Ma. On the other hand, systematic differences of the AMS parameters, such as the corrected anisotropy of magnetic susceptibility, shape parameter of ellipsoids, q factors, angles between the intermediate and minimum magnetic susceptibility directions and bedding, indicate that a dramatic transition of tectonic strain is most likely to occur at about 16 Ma (middle Miocene) in the Kuche depression. Taking into account the initiation o f C enozoic thrusting in the Kuche d epression i s at about 2 8-25 M a, we argue that the intensive Cenozoic thrusting in the Kuche depression is mainly happened during a period between the late Oligocene to middle Miocene.

济阳坳陷及其南缘奥陶系碳酸盐岩潜山储集性及控制因素

The main research area of this thesis is Jiyang Depression in the Bohaiwan Basin and its southern margin. The object formation is Ordovician carbonate. The research is based on the outcrop observation and measurement of Ordovician carbonate and the drilling data of the oilfield. The internal reservoir characteristics of carbonate buried hill and its distribution were studied by comprehensive methods of sedimentology, reservoir geology and structural geology and technics of cathodoluminescence(CL)3electron microprobe,casting and C O isotope analysis etc. The influence depth of paleokarst facies formed during the Paleozoic is discriminated as 36-84m. The sollution porosity is well developed in paleokarst facies of Ordovician carbonate and is an important type of internal reservoir of buried hill. It may be infered that the fractures may be formed mainly during the Mesozoic and Cenozoic, they were not developed during the early Paleozoic when only micro-fractures might be created. The carbon and oxigen isotope analysis shows that the calcite cements in the fractures of Ordovician carbonate and secondary solution pores were related with meteoric water and three stages of fractures were divided. The reservoir space of Ordovician carbonate are mainly secondary porosity, cavern and fracture. The development of structural fracture was controlled by the lithology and tectonic background. More fractures exist in dolomite than that in limestone. There are also more fractures near the fault and the axis of fold. The development of porous reservoir is mainly controlled by the lithology and diagenesis, especially dolomitization and dissolution. It also results in the heterogeneity vertically. So the lithology is the basic factor for the forming of internal reservoir of buried hill and the tectogenesis and diagenesis are key factors to improve it. The porosity in carbonate might experienced solution-cementation-resolution or recementation. The porosity evolution history was a kind of historical dynamic equilibrium. The internal reservoir of Ordovician carbonate is the comprehensive result of constructive and/or destructive diagenesis. The worm's eye maps of the early Paleozoic and middle-upper Proterozoic were plotted. It was inferred that the paleostress field evoluted from NNW to NW during the Mesozoic and Cenozoic. Three types of buried hills can be divided: C-P/Pzi, Mz/ Pzi and E/ Pzi. The unconformity of the buried hill of E/ Pzi type, comparatively, was formed and reconstructed latestly, t he p orous r eservoir c ould b e w ell p reseved. T his c ondition w as v ery favorable t o t he migration and accumulation of oil and gas and could form upstanding association of source-reservoir-cap rocks. The buried hills of Mz/ Pzi and C-P/Pz] type were took second place.

济阳地区深部结构与含油气性讨论

Oil and gas exploration of marine strata in China's Pre-Cenozoic residual basins is regarded as a worldwide puzzle because of existent problems and cruxes. Objectively speaking, the subsurface geologic structure is complicated, and the surface conditions of some areas are tough. On the other hand, there are still many problems to be solved in oil and gas exploration technologies of Pre-Cenozoic marine fades, and theoretic cognition about petroleum geology is not profound yet. Therefore, it is principal to explore integrated geophysical research ways of Pre-Cenozoic residual basins. Seismic prospecting and geophysical integrated interpretation technologies aimed at middle Paleozoic marine facies with deeper burial and complicated geologic conditions have not formed due to bad quality of deep strata data. Pre-Cenozoic strata, and especially extension, thickness and internal structure of Paleozoic strata can not be recognized from seismic profiles, so it is hard to systematically cognize structural features and oil-gas resources prospect of Pre-Cenozoic basins. To further investigation of fabric and structural features, basin prototype, formation and evolution pattern of Pre-Cenozoic basins, and also their control over formation, migration and aggregation of oil and gas, will play a guiding and promotive role in developing new surveying areas, selecting advantageous zones and predicting oil-gas resources.This paper follows the modem macrocontrol theory of "Region constrains local, deep strata controls shallow ones", and uses the integrated geophysical method of "One guide, two hinges, three combinations and multi feedbacks'*. Based on several years of geological and geophysical results of the Shengli Oilfield, and 14 newly-joint regional seismic profiles, deep structure and oil-gas bearing capacity of the Jiyang area are discussed and new cognitions are drawn as below.Seismic identification marks Tr, Tg, Tgl and Tg2 are established for importantPre-Cenozoic geological interfaces, and promoted to the whole Jiyang area.Through area-wide tracking and clogging of important seismic reflection marker,the isochronic framework of pre-Tertiary basin is set up in the Jiyang area for the firsttime, which is vital for basin research.Integrated with geological and geophysical research results, the Jiyang area isdivided into four first-order tectonic sequences- basement, lower tectonic layer,upper tectonic layer, and top tectonic layer. The basement and lower tectonic sequence which are related to Pre-Cenozoic are studied with emphasis.Through the research of regional seismic profiles, the point of view is given thatthe Kongdian Formation of Jiyang is structural transition period. The top-bottomunconformable interface of the Kongdian Formation is found out for the first time,and the basin model is determined primarily, which lay a basis for prototype basinresearch of the Jiyang Kongdian Formation.The distribution status of Middle-Paleozoic is delineated in the Jiyang area.The maximum thickness of Paleozoic lies in the top of the south declivity of half-graben. The thickness gets thinner towards the center of Mesozoic and Cenozoic half-graben basin, and even disappears. Structural action in the west-north affects the distribution of Paleozoic residual strata.6. The features of second-order tectonic sequence of the Jiyang depression isstudied and its evolution history of is rebuilt.Combined with the 5-stage evolution history of the China continent and structure evolution features of the Jiyang area, the structure sedimentary process since Paleozoic is divided into 5 periods - basement forming , Indosinian orogenic, Yanshan negative reversal, Himalayan extension and Neogene subsidence period.Combined with the research results of gravity, magnetic surveying and regionalprofiles, this paper brings forward the idea for the first time that the western boundaryof the Jiyang depression is the Ningjin-Yangpan fracture zone, and forms aside-column assemblage with the Wudi fracture zone.The opinion that under Middle-Cenozoic basins in the middle Jiyang area theremight superimpose an old residual basin is given for the first time. And if it is provedto be true, a new exploration space will be pioneered for Jiyang and even north China.There exists many types of tectonic-stratigraphic traps formed under piezotropy,extension and compound action in Pre-Cenozoic Jiyang. Therein all kinds of burialhills are the most important oil-gas trap type of Pre-Cenozoic, which should besurveyed layeredly according to the layout of oil sources.As such a new challenging project and field, the paper systematically analyses different geophysical responses of the Jiyang area, frames the deep structure of the area, and preliminarily recognizes the Pre-Cenozoic residual basins. It breaks through to a certain extent in both theory and practice, and is expected to provide new geophysical and geotectonic clues for deep exploration in Shengli.

中国东南部晚中生代以来的基性岩脉（体）的地质地球化学特征及其地球动力学意义初探-以江西省为例

基性岩脉具有特殊的地球动力学意义，一直是近十年来国际上研究的热点和重点。至今共举办过四次关于岩脉的国际专题大会，掀起了基性岩脉的研究高潮，分别从其分布、形态、古地磁、岩石学、地球化学、年代学和构造演化等方面进行了系统的研究。由于出露面积的关系，岩脉或岩脉群往往容易被人忽略，直到最近五年来中国东部中新生代基性岩脉的地球动力学意义才引起地质学者的关注，甚至有些学者指出中国东部中生代基性岩脉的研究可以填补国际上对此方面的空白。对中国东南部中生代基性岩脉的系统研究主要集中在粤北地区，琼南、福建沿海一带、湘东南、某些热液矿床的矿区的基性岩脉得到零星的研究，缺少对中国东南部更大范围的和系统的研究。另外，中国东南部晚中生代部分基性岩体与地壳拉张有关，但研究多集中于沿海一带，对于内陆基性岩体的构造应力体制是否与基性岩脉类似。本论文选择了江西省晚中生代以来的基性岩脉（体）为研究对象，运用矿物学、元素和同位素地球化学及K-Ar测年等研究方法，首次较为系统地研究了江西省晚中生代以来的基性岩脉、与地壳拉张有关的基性侵入岩体的地质地球化学特征，并利用对其形成时代、源区性质的研究来探讨中国东南部地壳拉张期次、地幔性质等地球动力学背景中的关键性问题。通过研究取得了以下几点初步认识：1系统地进行野外地质考察和采样，并收集前人的研究资料，发现江西省的基性岩脉的岩石类型主要为煌斑岩、辉-长辉绿岩、辉绿岩、辉绿（珍）岩等，相对较多，主要呈三条北北东向带状分布，分别为星子-上高-萍乡、德兴-余江-相山-吉安-上犹、草桃背-岩背-大吉山。2对江西省的基性岩脉和部分与地壳拉张有关的墓性岩体进行全岩K-Ar定年，结果表明，基性岩脉的形成时代为140-50Ma，再结合中国东南部发育的富碱侵入岩（包括A型花岗岩）和已发表的基性岩脉的年代学资料，作者认为中国东南部地壳拉张可能共有六期，分别为50-6OMa、90士Ma、100-11OMa、125士Ma、140士Ma、165～180 Ma。3对赣南车步辉长岩类的地质特征、矿物学和地球化学特征进行了研究，着重讨论它与沿海辉长岩类构造环境和源区性质的不同，研究表明它可能是中国东南部中侏罗世软流圈上涌、岩石圈伸展和地壳裂解的产物，而沿海白至纪辉长宕类的构造环境是弧后拉张盆地；车步辉味岩类的源区可能是未受到明显俯冲组分影响的富集地幔，而沿海白翌纪辉长岩类的源区可能包含较多俯冲组分。4对赣南大吉山地区和赣北地区早白圣世基性岩脉的地质地球化学特征进行了系统的研究，表明它们可能代表中国东南部早白至世初存在一次重要的岩石圈伸展和地壳拉张事件。但两者在岩石序列、微量元素、同位素方面存在明显不同，结合区域地质背景，认为造成赣南和赣北地区早白坐世的基性岩脉源区不同的可能原因是岩石圈地慢组成不同和／或形成基性岩脉的岩浆深度不同。5通过对江西省早白至世欧特里夫期（125士Ma）基性岩脉的地质、矿物学和地球化学特征进行研究，发现中国东南部的确存在早白至世欧特里夫期（125士Ma）基性岩脉，代表一次重要地壳拉张事件，其源区可能由亏损地幔、EMI和EMII地幔组成，后面两种类型地幔可能是先前受俯冲流体影响的成分不均一的富集岩石圈地幔。6通过对江西省早白至世未期（100-11oMa）和晚白至世（90士Ma）的基性岩脉（体）的地质地球化学特征进行研究，强有力的表明江西省存在100-110Ma、90士Ma两期地壳拉张，与粤北地区类似。本论文研究表明晚白至世的地壳拉张除了形成基性岩脉外，还形成同时代的基性岩体。这两期的基性岩脉（体）的源区可能由亏损地幔、EMI和EMll地幔组分组成，与（125士Ma）基性岩脉类似，但早白至世未期（100-110Ma）基性岩脉的源区可能含有相对较高的亏损地幔组分。7通过对江西省中部古新世的基性岩脉（体）的地质地球化学特征进行研究，发现了江西省中部的确存在50-60Ma地壳拉张事件。本期的基性岩脉（体）微量元素含量、MORB标准化模式和同位素与前面白至纪的基性岩脉（体）明显不同，软流圈参与其源区明显增多。8通过对中侏罗世以来基性岩脉（体）地质地球化学的系统研究，表明中国东南部晚中生代以来地幔性质发生了明显变化，总体变化趋势为亏损地幔代替富集地幔，这种过程与软流圈上涌、岩石圈伸展和地壳拉张有关：主要机制可能为岩石圈减薄，当然不排除其他机制。

Modelos de dinâmica da Terra aplicados à geologia de Portuga l: relevância da experimentação análoga no ensino e na divulgação da geologia

Tese de doutoramento, Geologia (Geodinâmica Interna), Universidade de Lisboa, Faculdade de Ciências, 2014

Assinatura tectono-sedimentar do auge da compressão bética em Portugal: a descontinuidade sedimentar Valesiano terminal-Turoliano

An Upper Miocene important sedimentary break can be accurately recognised in the Portuguese basins and is reflected by a drastic palaeogeographic change in relation to a large-scale tectonic event of probable uppermost Vallesian-Turolian (9,5 Ma; middle Tortonian) age. The characterisation of the sedimentary record of this tectonic event, as well as its relations with interpreted active faults is made for different situations: Douro (NW border), Mondego, Lower-Tagus and Sado Tertiary basins. The sedimentary record, considered upper Tortonian-Messinian ? (uppermost Vallesian-Turolian ?) is interpreted mainly as endorheic alluvial fans (internal drainage), developed along active NNE-SSW indent-linked strike-slip faults and NE-SW reverse faults. At NE Portugal, proximal fluvial systems of an endorheic hydrographic network drained eastwards to the Spanish Duero interior Basin. The main evidences of the betic compression clímax in Portugal mainland are presented; the interpreted active tectonic structures are in accordance with an intense NNW-SSE crustal shortening, but some regional differences are also documented.

Estratigrafia e interpretação paleogeográfica do Cenozóico continental do norte de Portugal

Palaeogeographic and tectono-sedimentary interpretation of northern Portugal, in which previous studies (geomorphology, lithostratigraphy, mineralogy, sedimentology, palaeontology, etc.) were considered, is here proposed. Cenozoic shows different features according to its morphotectonic setting in the eestern region (Trás-os-Montes) or near to the Atlantic coast (western region, Minho and Douro Litoral areas). Although in the eastern region the sedimentary record is considered late Neogene, in some places Paleogene (?) was identified. This oldest record, represented by alluvial deposits, was preserved from complete erosion because of its position inside Bragança-Vilariça-Manteigas fault zone grabens. Later sedimentary episodes (upper Tortonian-Zanclean ?), represented by two allostratigraphical units, were interpreted as proximal fluvial braided systems of an endorheic hydrographic network, draining to the Spanish Duero Basin (eastwards); nowadays, they still remained in tectonic depressions and incised-valleys. Later on, eastern sedimentation becomes scarcer because Atlantic fluvial systems (e.g. the pre-Douro), successively, captured previous endorheic drainages. The proximal reaches of the allostratigraphic unit considered Placencian is recorded in Mirandela (western Trás-os-Montes) but the following fluvial episode (Gelasian-early Pleistocene ?) was already documented in east Trás-os-Montes, preserved in high platforms and in tectonic depressions. Placencian and Quaternary sedimentary records in the western coastal zone, mainly represented by terraces, are located in the Minho, Lima, Alverães, Cávado and Ave large fluvial valleys and in the Oporto littoral platform. In conclusion, northern Portugal Tertiary sedimentary episodes were mainly controlled by tectonics, but later on (Placencian-Quaternary) also by eustasy.

Estratigrafia sismica do cenozóico na plataforma continental algarvia: interpretação do controle tectónico da sedimentação

The interpretation of 64 seismic reflection profiles in the Algarve continental platform (36º 20'-37º 00' paralels and 7º 20'-8º 40' meridians) calibrated with five petroleum exploration wells, with the identification of the geometric relations between six Cenozoic seismic units (B to G) and tectonic structures, allowed the construction of sucessive time-isopach maps (twt/s) and detailed interpretation of the geologic evolution. Two major tectonic structures were identified: a) the Portimão-Monchique fracture zone (striking N-S); b) an off-shore NW-SE fault zone, probably the S. Marcos-Quarteira fault. This accident separates two tectonic domains: the western domain (with N-S and E-W predominant structures and, secondarily, NW-SE and NE-SW) and the eastern domain (dominated by WSW-ENE, NW-SE, NE-SW, NNE-SSW and NNW-SSE structures). A persistent halokinetic activity had two major moments: a) sin-C unit; b) sin- and post-E unit. An increasing flexuration of the margin was identified, with spacial and temporal variation of the subsidence. The tectonic regime is considered as generally compressive, but the interpretation of the successíve stress-fields is rendered dificult by the existence of tectonic sub-domains and evaporitic structures.

The Teggiolo zone: a key to the Helvetic-Penninic connection (stratigraphy and tectonics in the Val Bavona, Ticino, Central Alps)

The Teggiolo zone is the sedimentary cover of the Antigorio nappe, one of the lowest tectonic units of the Penninic Central Alps. Detailed mapping, stratigraphic and structural analyses, and comparisons with less metamorphic series in several well-studied domains of the Alps, provide a new stratigraphic interpretation. The Teggiolo zone is comprised of several sedimentary cycles, separated by erosive surfaces and large stratigraphic gaps, which cover the time span from Triassic to Eocene. At Mid-Jurassic times it appears as an uplifted, partially emergent block, marking the southern limit of the main Helvetic basin (the Limiting South-Helvetic Rise LSHR). The main mass of the Teggiolo calcschists, whose base truncates the Triassic-Jurassic cycles and can erode the Antigorio basement, consists of fine-grained clastic sediments analogous to the deep-water flyschoid deposits of Late Cretaceous to Eocene age in the North-Penninic (or Valais s.l.) basins. Thus the Antigorio-Teggiolo domain occupies a crucial paleogeographic position, on the boundary between the Helvetic and Penninic realms: from Triassic to Early Cretaceous its affinity is with the Helvetic; at the end of Cretaceous it is incorporated into the North-Penninic basins. An unexpected result is the discovery of the important role played by complex formations of wildflysch type at the top of the Teggiolo zone. They contain blocks of various sizes. According to their nature, three different associations are distinguished that have specific vertical and lateral distributions. These blocks give clues to the existence of territories that have disappeared from the present-day level of observation and impose constraints on the kinematics of early folding and embryonic nappe emplacement. Tectonics produced several phases of superimposed folds and schistosities, more in the metasediments than in the gneissic basement. Older deformations that predate the amplification of the frontal hinge of the nappe generated the dominant schistosity and the km-wide Vanzèla isoclinal fold.